Proper measurements for height and width of mig weld beads

November 21, 2020 1:06 PM

I'm learning to mig weld. I practice a lot and have read a fair amount about it online and in several books. I have found diagrams showing acceptable and unacceptable bead profile shapes, but I haven't found guidelines which specify the acceptable bead height/width measurements for a given thickness measurement of metal being joined. That is, I'm looking for a source that says, with a math formula or in a table: if your base metal is "x" thickness, then for each joint type your bead should be approx. "this" wide and "this" tall (assuming proper fit up, penetration, and no defects). I already cut and etch to check penetration, profile shape, and defects, but I would like to know if my welds are correctly sized. (I won't be taking a class and I don't know anyone who is a certified welder to ask these questions to.) Thanks!
posted by atm to Home & Garden (4 answers total)

Best answer: It kind of depends, but there's generally no reason to have a weld be thicker than either of the base materials it's joining. If you're doing things where the weld dimensions are specified, this might be useful.
posted by LionIndex at 2:50 PM on November 21, 2020

Best answer: The answer will depend upon what welding standard you are attempting to comply with. So for example, in AWS D1.1 fillet welds are covered by Table 5.7 (that's a retype of the table, not the real table itself), and then there are other tables for the various geometries and weld processes. If you're not doing structural welding, then at minimum complying with D1.1 will mean you've got a certain level of overkill in your welds, which is usually good so maybe go for D1.1 unless there's a reason not to?

...and upon that point, let us keep in mind that I'm not familiar with sheet metal welding, process plumbing welding, or any of the others, and their answers may differ (btw, for standards purposes MIG is a subtype of GMAW welding).
posted by aramaic at 5:20 PM on November 21, 2020 [1 favorite]

Response by poster: My thanks to both of you.

Aramatic, thanks for pointing me to AWS D1.1. (for future searchers, the version from year 2000 is here)

I'm going to keep looking through it, but so far all I have seen is that bead sizes are to be specified by the engineer or contractor.
posted by atm at 3:55 AM on November 25, 2020

Yes, in structural welding the engineer is generally involved, as the weld must be designed with due consideration of the loads it will be carrying, and only the Engineer Of Record can specify what those loads are. Here's a decent look at some of the considerations (see for example Fig.8 vs. Fig.9); pretty much anything you read by Duane Miller will be worth your time (in terms of welding) and he's written like a bazillion articles (including many more in that same magazine I just linked).

For welding that isn't involved in structural engineering the same general principles apply; someone has to decide how the loads are going to be transferred through the welded joint, and that person gets to decide how the joint geometry will work.
posted by aramaic at 9:06 AM on November 25, 2020